1. Field of the Invention
The present invention relates to a storing method of storing, with a small memory capacity, substantial data that is configured by integrating shape data and physical property data so that CAD and simulation can be integrated. Specifically, the present invention relates to a method and program of converting three-dimensional shape data into internal data of a cell by oct-tree division.
2. Description of the Related Art
In the field of leading-edge research and technology development, as the research and technology is highly developed and complicated, it becomes inevitable to perform a process of trial and error many times, so that a risk of failure in the development process is raised. In order to lead in science and technology, it is very important to avoid such a risk as much as possible, and to make innovative advancement and efficiency promotion.
At present, in the field of research and technology development, CAD (Computer Aided Design), CAM (Computer Aided Manufacturing), CAE (Computer Aided Engineering), CAT (Computer Aided Testing) are used as simulation means for designing, processing, analyzing, and testing, respectively.
Further, the C-Simulation (Corporative Simulation) that is successive simulation, A-CAM (Advanced CAM) that takes processing into account, and D-fabrication (Deterministic Fabrication) that achieves ultimate accuracy will become widespread by the present invention.
When using the above-mentioned simulation means, data of a target object is stored by CSG (Constructive Solid Geometry) or B-rep (Boundary Representation).
However, in the case of CSG, an entire target object is stored as an aggregation of minute solid models. Accordingly, the data amount becomes large, and simulation means (software, for example) handles a large amount of data. Therefore, there is a problem in that even a large computer takes much time to perform data analyzing.
In the case of B-rep, since the target object is represented by the boundary, the data amount becomes small. However, the information about the inside of the boundary surface cannot be obtained directly, and there is a problem in that the data itself is not suitable to deforming analysis.
Furthermore, according to the above-mentioned conventional data storing means, each time heat/fluid analysis, largely deforming analysis of a solid, or coupled analysis of them is performed, the data is divided into meshes suitable to the analysis, and a finite element method or the like is used. The result of the analysis can be displayed, for example, but it is difficult to integrate CAD and simulation. Accordingly, there is a problem in that respective processes of designing, analyzing, processing, assembling, testing, and so on cannot be managed by using the same data.
In other words, the conventional Solid/Surface-CAD (hereinbelow, referred to as S-CAD) has the following problems.
(1) The data communication, and internal converting operation of the data are poor (that is, there is a problem of a numerical value error and a process method).
(2) The data cannot be applied directly to the simulation (that is, since the data does not include the internal data, the meshes need to be generated).
(3) It is not possible to consider how to perform the processing by CAM (there is only a final shape).
Further, there are the following problems regarding the processing.
(1) It is not possible to represent the processing (the aid of rough processing and aid of process designing are inadequate).
(2) The data cannot cope with a new processing method such as laser processing and ultra front edge processing (that is, other processing except cutting processing cannot be performed, and numerical value accuracy is inadequate).
(3) A processing method cannot be selected when a target object is a complex having different material properties inside.
In order to solve the above problems, prior to the present patent application, the inventor(s) of the present invention made the invention “Method of Storing Substantial Data Configured by Integrating Shape Data and Physical Property Data” that was filed as Japanese patent application No. 2001-25023).
According to this prior invention, as schematically shown in FIG. 1, external data including boundary data of a target object is divided into rectangular parallelepiped cells by oct-tree division. Each of rectangular parallelepiped cells has boundary faces orthogonal to each other. Then, each cell is classified into an internal cell 13a positioned inside or outside the target object or a boundary cell 13b including a boundary face. In FIG. 1, the reference numeral 15 designates a cut point.
With this prior invention, various physical property values are stored in respective cells so that the integrated substantial data of the shape data and the physical property data can be stored by using a small memory capacity. Thereby, it is possible to achieve integral management of shape data, structure data, physical property data, and history of a target object. Accordingly, data about a series of processes including designing, processing, assembling, testing, evaluating, and the like can be managed by the same data, and CAD and simulation can be integrated.
In the case of this storing method (hereinbelow, referred to as “volume CAD” or “V-CAD”) of storing substantial data, the boundary data for restructuring the boundary surface of the three-dimensional shape data (external data) needs to be held in the boundary cell.
If the boundary data cannot maintain continuity with the neighboring cells, when the surface of the cell is divided into triangle-shaped meshes, a gap (crack), a minute triangle, or a thin long triangle is generated. Therefore, a problem arises in that accurate simulation cannot be performed.
Meanwhile, there is a known method (crack patch method) of filling up a gap between the triangle meshes that is generated between different size volumes. However, in this method, the gap is simply filled up so that the triangle meshes sharing the edge thereof and making a sharp angle therebetween are generated at the position where the original surface is smooth. In order to solve this problem, Japanese Laid-Open Patent Publication No. 2001-22961 proposes “Method of Generating Same Phase Surface from Non-Uniformity Volume Model”. However, in this method, application of different model volume CAD is difficult, and the process of this method is complicated.